Yasmineh W G
Department of Laboratory Medicine and Pathology, University of Minnesota School of Medicine, Minneapolis 55113.
Clin Biochem. 1988 Aug;21(4):239-43. doi: 10.1016/s0009-9120(88)80007-9.
We describe a simple, kinetic method for the determination of serum guanase activity that involves enzymatic coupling to xanthine oxidase and measurement of the rate of uric acid formation by spectrophotometric monitoring of the absorption at 300 nm. At this wavelength, the absorption of uric acid is about 80% of its maximal absorption at 293 nm, but the difference in molar extinction coefficient between guanine and uric acid is similar (9,000 at 293 nm vs 8,400 at 300 nm). There are three advantages to the use of the higher wavelength: first, the absorption of serum proteins is only one third of the absorption at 293 nm resulting in a significant reduction in noise level. Second, the lower absorption of serum proteins allows increasing sensitivity of the assay by increasing the amount of serum in the reaction mixture. Third, the higher wavelength allows the use of automated centrifugal analyzers that are generally not designed for measurements below 300 nm. The between-day coefficient of variation was 5.8% (n = 27) at an activity of 17 U/L and 8.2% at an activity of 2 U/L. The reference range for 50 sera from males and females was 0.4 to 1.8 U/L (n = 50; mean +/- 2SD). The method is linear to 40 U/L.
我们描述了一种简单的动力学方法来测定血清鸟嘌呤酶活性，该方法涉及酶偶联至黄嘌呤氧化酶，并通过分光光度法监测300nm处的吸光度来测量尿酸形成速率。在此波长下，尿酸的吸光度约为其在293nm处最大吸光度的80%，但鸟嘌呤和尿酸之间的摩尔消光系数差异相似（293nm处为9000，300nm处为8400）。使用较高波长有三个优点：第一，血清蛋白的吸光度仅为293nm处吸光度的三分之一，从而显著降低了噪声水平。第二，血清蛋白较低的吸光度允许通过增加反应混合物中血清的量来提高测定的灵敏度。第三，较高的波长允许使用通常未设计用于300nm以下测量的自动离心分析仪。在17U/L的活性下，日间变异系数为5.8%（n=27），在2U/L的活性下为8.2%。50份男性和女性血清的参考范围为0.4至1.8U/L（n=50；平均值±2SD）。该方法在40U/L范围内呈线性。
